Taku Nonomura | Japan Aerospace Exploration Agency (original) (raw)

Papers by Taku Nonomura

International Journal of Heat and Fluid Flow, 2015

21st AIAA/CEAS Aeroacoustics Conference, 2015

22nd AIAA Computational Fluid Dynamics Conference, 2015

ABSTRACT A two-fluid AUSM+-up numerical flux function with the exact (Godunov) Riemann solver for... more ABSTRACT A two-fluid AUSM+-up numerical flux function with the exact (Godunov) Riemann solver for the stratified flow model concept by Chang et al. (2007) has been extended for simple and robust computations of compressible multiphase flows. The present method replaces the Godunov part with the HLLC approximate Riemann solver with no-iteration procedure in a very simple manner: This two-fluid HLLC has been inspired by the work by Hu et al. (2009), but used in a totally different way. Numerical tests demonstrate that the present two-fluid AUSM+-up is, if only velocity and pressure in the middle zone are computed by HLLC, as robust as the original, Godunov-combined AUSM+-up, despite being free from iterations and convergence criteria.

Mathematical Problems in Engineering, 2015

Progress in Flight Physics – Volume 7, 2015

TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN, 2014

$Research paper thumbnail of Effects of Burst Frequency and Momentum Coefficient of DBD Actuator on Control of Deep-stall Flow around NACA0015 at Rec=2.6x10^{5}$

52nd Aerospace Sciences Meeting, 2014

In this study, multiobjective design exploration for a rocket launch site is conducted using the ... more In this study, multiobjective design exploration for a rocket launch site is conducted using the evolutionary computation with the large eddy simulation to understand the acoustic characteristics associated with various launch sites and find design information such as trade-off relation among objective functions. The launch site is described by the curved surface. The flat plate inclined with 45 degree is considered as the reference configuration. The objective functions of multiobjective aeroacoustic design optimization are, 1) minimization of averaged sound pressure level near the payload fairing, 2) minimization of maximum pressure on the curved surface of the rocket launch site, and 3) minimization of the difference of the curved surface from the flat plate inclined with 45 degree. Threedimensional compressible Navier-Stokes equations are solved with the modified weighted compact nonlinear scheme. The total number of evaluation in multiobjective evolutionary computation is 2500, and the evaluation of one configuration necessitates the use of 130 nodes(1040 total cores) using "K" supercomputer. Firstly, the analysis of non-dominated solutions clearly shows that there are various trade-off relations and correlations among the objective functions. Furthermore, the analysis of flow fields shows that as the curved surface around the impingement region becomes steeper, the acoustic waves generated from the impingement region weaken. This is because the curved surface becomes steeper, the separation bubble near the impingement region becomes smaller, and finally disappears. The proper orthogonal decomposition(POD) analysis is conduced to extract the characteristic modes from characteristic non-dominated solutions.

Volume 1B, Symposia: Fluid Machinery; Fluid Power; Fluid-Structure Interaction and Flow-Induced Noise in Industrial Applications; Flow Applications in Aerospace; Flow Manipulation and Active Control: Theory, Experiments and Implementation; Fundamental Issues and Perspectives in Fluid Mechanics, 2013

ABSTRACT The flow over a National Renewable Energy Laboratory S825 airfoil was simulated for a ch... more ABSTRACT The flow over a National Renewable Energy Laboratory S825 airfoil was simulated for a chord Reynolds number of 7.5×105 and an angle of attack of 22.1 deg. These conditions approximately matched a blade element condition of 75% radius of 42-m-diameter wind turbine operating 2.5 rpm under a free-stream of 10 m/s. Computed flow of the uncontrolled case characterized massive separation from near the leading edge due to high angle of attack. With the active flow control by a dielectric barrier discharge plasma actuator, separation was reduced and the lift-to-drag ratio increased from 2.25 to 6.52. Impacts of the plasma actuator on the shear layer near the leading edge were discussed. Direct momentum addition provided by the case setup of plasma actuator considered in current study seemed to be a dominant factor to prevent the separation of shear layer near the leading edge rather than influence of small disturbances induced by the plasma actuator operated in a burst modulation. However, due to the high angle of attack and the thick airfoil, the control authority of the plasma actuator with the setup (i.e. the operating condition and number of plasma actuators installed on the wing surface) considered was insufficient to completely suppress the separation over the NREL S825 airfoil.

TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN, 2012

We analyze the asymmetric vortices in the flow over a slender body at high angle of attack by num... more We analyze the asymmetric vortices in the flow over a slender body at high angle of attack by numerical simulations aiming a proportional control of the side forces generated by vortices with a device such as dielectric barrier discharge (DBD) plasma actuator. With regard to the computational method, Reynolds averaged Navier Stokes/large-eddy simulation hybrid method is adopted with high-order compact spatial difference scheme. The grid convergence analysis is firstly conducted and the results show that the computational grid adopted in this study is fine enough for qualitative discussion. The total number of the grid point is 411 million points. Then, the effects of bump height on flow fields and aerodynamic characteristics are discussed. Note that bump is added near the body apex to simulate the symmetry-breaking imperfection. As a higher bump is adopted, stronger asymmetry is observed in the flow fields. On the other hand, side-force has nonlinearity with the bump height.

51st AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition, 2013